The present invention relates generally to disc drive data storage devices, and more particularly without limitation to temperature compensation for thermal pole tip protrusion between a slider and a disc.
After a disc drive is energized, it warms up and has a temperature rise. In particular, there are large temperature rises in the heads used in a disc drive. The heads include magnetic transducers deposited on slider substrates. The magnetic transducers carry read/write currents that generate heat in the heads. The temperature rise in the heads is large because the heads have a small surface area in relation to the amount of heat that is dissipated in the magnetic transducers.
The magnetic transducers have a higher coefficient of thermal expansion (CTE) than the slider substrates. As temperature increases, the magnetic transducers thermally expand at a greater rate than the slider substrates. The thermal expansion causes the pole/shield tips of the magnetic transducers to protrude with respect to an air bearing surface of the slider substrate. At higher temperatures, the pole/shield tips protrude and are closer to the media and the transducer-media spacing (pole tip to disc spacing) is reduced. If the transducer-media spacing at lower temperature is not large enough, the protruded pole/shield tips hit the media at higher temperature.
To avoid transducer-media contact at higher temperatures, the fly height at lower temperatures is kept relatively large. This large fly height at lower temperatures, however, undesirably limits the electrical performance of transducers, particularly the areal bit density (gigabits per square inch) that can be achieved.
A method and apparatus are needed that correct for the thermal pole tip protrusion at higher temperatures.
Disclosed are embodiments of a disc drive that include a disc, a voice coil motor and a beam extending from the voice coil motor to a gimbal point. A slider in the disc drive receives a load force from the gimbal point and flies over the disc at a fly height (FH). The slider has a pole tip protrusion that is temperature sensitive. A strut in the disc drive couples between the beam and the slider. The strut includes a yielding bend section (YBS).
First and second deposits of shape memory alloys (SMA) are deposited on the yielding bend section (YBS). The first and second deposits have corresponding first and second transformation temperature ranges that differ from one another. The first and second deposits of shape memory alloy change shape in their corresponding transformation temperature ranges. The first and second deposits of shape memory alloy provide temperature compensation to the fly height between a leading edge of the slider and the disc. By compensating the fly height between the leading edge of the slider and the disc, the ambient temperature sensitivity of the pole tip to disc spacing is reduced.
These and various other features as well as advantages which characterize embodiments of the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.